There is an increasing demand for optical networks and optical communication between nodes of such networks, due to the increased global demand for high speed data exchange. Such optical communication systems need one or more optical cross-connect switches at each node to switch the received optical signals to a desired destination node in the optical network. For example, a high bandwidth transparent optical communication network for a free space satellite communication system requires a high bandwidth optical switch to establish the proper connections on each satellite between input and output optical signals, and a filter to reduce Amplified Spontaneous Emission (ASE) noise. However, these various optical components increase the weight of the payload and reduce the performance of the optical switch.
There are several optical cross-connect switch designs that have been implemented for the ground fiber optics market. Moreover, optical demultiplexers and Fabry-Perot comb filters are known, but there has not been any attempt to develop an optical device that combines the full required (optical) capabilities of these various optical devices. Current Optical Cross-Connect (OXC) Switch technology has several limitations when considered for space systems. First, these systems are designed for use on the ground, where repair or replacement is possible. In space, graceful degradation is essential, with subsystems designed with enough redundancy that operation can continue as minor damage is inflicted by the environment, especially by the penetrating radiation. Future-proofing is even more important in space than on the ground, as each satellite needs to support a mean mission duration of at least 10 years, before being replaced by a new satellite.
Second, because of the large separation between satellites, the received signal strength is typically at least 70 dB weaker than the transmitted signal. This means that the signal must be amplified by at least that much before being relayed to the next node. ASE generated in the low-noise pre-amplifier needs to be suppressed as soon as possible, but the possibility that the channel spacing will need to change over time makes it impractical to use a conventional comb filter to eliminate the ASE. This includes matching the width of the communication channels as precisely as possible in the switch, and directing all photons in unused channels to a photon trap, which may use Carbon Nano-Tube (CNT) forests to absorb the highest possible fraction of those photons. A third limitation is the inability to perform multicasting or signal splitting. In some cases this can be deferred to a later signal splitter element in the output fiber lines, but this offers very limited flexibility.